V1 Chubbs' extended track build #300, 2007 SS/SC donor

[Chubbs]

Oh, and I'll add another shout out for my headlights:

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I know I posted them above, but I can't stress how happy I am with them. I've actually used them in the dark now, and they are impossibly bright for how tiny they are. I really didn't expect them to do much, since they are about the size of a deck of cards (maybe two decks stacked on each other). But they throw bright light down the road just like a full size truck would. I'm amazed. The low beams are yellow, which is weird at first but I've gotten used to it. The high beams are bright white. For $70, I don't think you can do any better.

And no, I'm not affiliated with them or anything.

 

[Chubbs]

It's been a long time since an update, but it's also been a long time since good weather. The car has been sitting in the cold garage for a while now.

This past weekend though, I did my first Auto X in it, with the porsche club in KC (the yellow boxster in the pic is also mine, and the cheapest way into the porsche club ) What a blast. I'm still fighting alignment issues, which makes it a real handful to drive. It's super-darty, and dives for a corner on turn in as if it has a mind of it's own. But hey, turn-in is a good thing in Autocross, right?

Times got progressively better throughout the day, and I ended up in 4th place with 1 run left to go (it's not a competitive event, but we all know what the times are). I had a great run going, potentially the best of the day, when I spun it like a top. Charging into one of the final corners, on the brakes, and the rear end just came around in a heartbeat. I never had a chance to save it. I know mid engine cars (including the boxster) will sometimes rotate under braking, but I've never had one snap oversteer so quickly before.

I'm blaming the rear end for the alignment issues. The toe plates I have used for alignment, I think were catching the "bulge" at the bottom of the tire (where it smooshes out against the pavement), and therefore I was getting different numbers everytime I measured toe-in. By putting a 2x4 under the toe plates, I elevated them enough that they are now squarely against the tire sidewall, and should be more accurate. I made a couple of adjustments, and hopefully I can get the car a bit more stable at speed.

If not, I'm going for front downforce. I already have the carbon fiber plate to use as a splitter, and have some 3d printed airfoil elements to mount on it. Because racecar.

 

[Scott #321]

I have been fighting the snap oversteer as well braking, acceleration, or coast. I'm still experimenting with setup.

 

[JBINTX]

It's been a long time since an update, but it's also been a long time since good weather. The car has been sitting in the cold garage for a while now.

This past weekend though, I did my first Auto X in it, with the porsche club in KC (the yellow boxster in the pic is also mine, and the cheapest way into the porsche club ) What a blast. I'm still fighting alignment issues, which makes it a real handful to drive. It's super-darty, and dives for a corner on turn in as if it has a mind of it's own. But hey, turn-in is a good thing in Autocross, right?

Times got progressively better throughout the day, and I ended up in 4th place with 1 run left to go (it's not a competitive event, but we all know what the times are). I had a great run going, potentially the best of the day, when I spun it like a top. Charging into one of the final corners, on the brakes, and the rear end just came around in a heartbeat. I never had a chance to save it. I know mid engine cars (including the boxster) will sometimes rotate under braking, but I've never had one snap oversteer so quickly before.

I'm blaming the rear end for the alignment issues. The toe plates I have used for alignment, I think were catching the "bulge" at the bottom of the tire (where it smooshes out against the pavement), and therefore I was getting different numbers everytime I measured toe-in. By putting a 2x4 under the toe plates, I elevated them enough that they are now squarely against the tire sidewall, and should be more accurate. I made a couple of adjustments, and hopefully I can get the car a bit more stable at speed.

If not, I'm going for front downforce. I already have the carbon fiber plate to use as a splitter, and have some 3d printed airfoil elements to mount on it. Because racecar.

Keep posting your results/thoughts in the Goblin. We all can learn from it!

 

[Chubbs]

It was tail-happy under throttle as well, but I'm used to that with rear drive cars. it's at least controllable with throttle application.

Mid corner, I was pleasantly surprised by how neutral it was. I know the phrase is overused, but it was like a big gokart. The front end would sort of skip around, then it would bite, and then the rear slid out under power. It was all very nice.

Until the rear end turned into roller skates under braking. Oddly, it only happened once. The other times I was on the brakes, the fronts would lock up, and the rear stayed planted. I'm not sure why it stepped out just once, and not the other times, other than this was one of the few times I was really trail braking.

For what it's worth, I'm running a base-model rear swaybar on it. Tires are stock cobalt size, Bridgestone RE-71Rs. If I can't get the rear to stick well enough, I may go to a staggered tire setup.

 

[Rauq]

Have you tried running it without the rear bar?

 

[JBINTX]

It was tail-happy under throttle as well, but I'm used to that with rear drive cars. it's at least controllable with throttle application.

Mid corner, I was pleasantly surprised by how neutral it was. I know the phrase is overused, but it was like a big gokart. The front end would sort of skip around, then it would bite, and then the rear slid out under power. It was all very nice.

Until the rear end turned into roller skates under braking. Oddly, it only happened once. The other times I was on the brakes, the fronts would lock up, and the rear stayed planted. I'm not sure why it stepped out just once, and not the other times, other than this was one of the few times I was really trail braking.

For what it's worth, I'm running a base-model rear swaybar on it. Tires are stock cobalt size, Bridgestone RE-71Rs. If I can't get the rear to stick well enough, I may go to a staggered tire setup.

What tires are you running?
Do you have a brake proportioning valve installed?

 

[Chubbs]

Have you tried running it without the rear bar?

I have not, at least not in anger. I have run it on the street without the rear bar, but obviously that's a very different situation from an AutoX.

I'm going to get the alignment figured out, and maybe run it again before disconnecting the rear sway bar. ALthough I agree disconnecting it would help, I'm also afraid of changing too many things at once, and then having no idea what any one change actually did to the handling of the car. I try to change 1, or maybe 2 things at a time and see what happens.

What tires are you running?
Do you have a brake proportioning valve installed?

Bridgestone RE-71Rs. No brake proportioning valve, it's all stock goblin stuff. In a straight line, the fronts lock up way before the rears do. But at the limits of lateral traction, who knows?

 

[JBINTX]

I have not, at least not in anger. I have run it on the street without the rear bar, but obviously that's a very different situation from an AutoX.

I'm going to get the alignment figured out, and maybe run it again before disconnecting the rear sway bar. ALthough I agree disconnecting it would help, I'm also afraid of changing too many things at once, and then having no idea what any one change actually did to the handling of the car. I try to change 1, or maybe 2 things at a time and see what happens.



Bridgestone RE-71Rs. No brake proportioning valve, it's all stock goblin stuff. In a straight line, the fronts lock up way before the rears do. But at the limits of lateral traction, who knows?

I would highly suggest you think about doing this. The Goblin’s weight and balance is far different than an ordinary car.
All the Houston gang have had vastly improved breaking results.

Add-on brake proportioning valve

Doing some autocross, I found that you jamb on the brakes and the fronts lock instantly. Unless you are in a panic stop on the street, you’ll never experience this. At autocross, you find out quickly that you cannot jamb down on the brakes. After doing some research, I decided to decrease the...

dfkitcar.com

 

[Rttoys]

Yep. Brake prop will make a huge difference and better tires will help. I ran autocross on 245s and did very well. I have stepped up to 245 front and 275 rear. That made a huge difference. I found running the “comfort ride” base model sway bar helped a lot at autocross, too. Suspension settings and tire pressure are key too.

 

[Chubbs]

After much wailing and gnashing of teeth, finally some success!

Replacing the rear ball joints basically "cured" my handling woes. It's still not a mercedes S class on the highway, but it drives straight, and doesn't try to put me in the ditch every time I wiggle the steering wheel. I can change lanes without worrying much about it.

Yesterday I did another autocross with the local Porsche club, and posted the best time of the day. Perhaps more importantly, it feels right at home on the autocross course. The nervousness on the highway turns into nimbleness. On-power corner exits are a highlight. It will actually tighten it's line under power, and I found myself adding power earlier and earlier with no ill effects coming out of corners.

Mid corner feels pretty neutral, though I think it defaults to understeer just barely. It's probably for the best, for now. I don't want to wrap it around a tree before I have a chance to enjoy it. I really want to do a staggered width tire setup, both because it looks cool, and because it seems like it should need more rubber in the rear with all the weight and power back there. But for now, the stock cobalt size is working well (it's just ugly).

Corner entry though, is a bit of a mess. Trail braking is impossible, because the fronts lock waaaay too early. I can't actually the rear brakes do anything. A brake proportioning valve is sitting in the garage right now, ready to go on.

 

[Chubbs]

I have stepped up to 245 front and 275 rear. That made a huge difference. I found running the “comfort ride” base model sway bar helped a lot at autocross, too. Suspension settings and tire pressure are key too.

I'm curious how the staggered setup compared to the square setup.

A short wheelbase, high horsepower rear drive car like the goblin can be tricky. Understeer is ok with me, so long as it's not overwhelming. It's nice to unstick the rear once in a while when you're doing it intentionally. Can you still un-stick yours with those big tires in the rear?

 

[Lndshrk Steve]

Yes, mid engine cars LOVE to be on power thru the corners. And get the brake proportioning valve on. That will help to induce rotation at the turn in, and that helps point the car.
PS You stop the rotation with the throttle.

 

[Rttoys]

These cars are very tricky, all the way around. Its all experimental and we are still figuring out the details. You are now part of the experiment.

 

[Chubbs]

It's been awhile since I updated this, but I got a lot done today. It's amazing how productive I can be when the kids are at grandma's, and the wife is busy doing other things.

Some of you may know from other threads I was experiencing some high iat2 temperatures, in the neighborhood of 150°, even while idling. I believe the heat exchanger was absorbing heat from the radiator, which is relatively close to it. I ended up installing an auxiliary heat exchanger behind the passenger seat. Although air flow is mostly blocked by the passenger seat, it's still managed to lower iat2 temperatures by at least 10°, and probably 20 in most cases. Just cruising around, temperatures are normally around 125°, which seems completely acceptable. Under heavy load, they get up to the 145/150 degree range, which isn't ideal but still seems acceptable. See photos from mounting. I used a couple of factory installed mounting points behind the seat along with a piece of angled aluminum.

I need to get a 90° elbow for one of the hoses, as the inside hose is bent too sharply and kinks a little. It doesn't seem to affect flow, but an elbow would be better. It's a work in progress but I'm pleased with the results so far.

 

[Chubbs]

Next up, I mounted a carbon fiber front splitter. The splitter itself is a wet layup piece of carbon that I made in the garage with carbon fabric, and epoxy resin. Since the middle layer of it is made of a fabric material that absorbs a lot of resin, it's not the lightest weight possible. But it's still weighs next to nothing, and is crazy strong.

Mounting, unfortunately, turned out less than ideal. It's somewhere between "I guess that's good enough", and "that'll never work". The front supports just aren't far enough in front, and the very front flexes quite a bit. It's not terrible, but I wouldn't dare stand on it. It'll support maybe 50lbs, and that's a stretch.

Still, it looks amazing. I have test driven yet, but I hope to tomorrow.

 

[Robinjo]

Did you lay the carbon in that design or make a big sheet and then cut out the design after?

 

[Chubbs]

I just made a big sheet, about 34"x38" if I remember right. Sandwiched between two large pieces of glass to make the final product smooth. There's some porosity in it because I didn't have equipment for a vacuum seal, but its minor.

Then I marked it all up in the right shape, and cut it out with a grinder/cutoff wheel.

Also, it works! It isn't a night and day difference, but the front end is more planted. The alignment made it feel 90% more planted than it was before, and I'd say this little bit of downforce added another 10%. It definitely won't fix a squirrely car, but it will help a bit.

 

[Chubbs]

Track update! The goblin saw the track for the first time last week (Heartland Park, Topeka). I've autocrossed it before, but never had it on the big track. I ran with the Advanced group because intermediate was full, and it worked out fine. I was one of the slower guys, but not the slowest, and the A group generally knows what they are doing so it was a non issue.

THe goblin did fine, but more tweaks are needed (aren't they always?). It didn't explode, and I didn't crash it, so it was a successful day. I did spin it once though....lift off oversteer is real! Any MR2 driver will tell you, don't lift mid corner. It applies to the goblin. It will snap oversteer in a heartbeat, and I was too slow to catch it once. I altered tire pressures a bit, and firmed up the front suspension a bit, and it helped the issue. I suspect the real answer is to put on a staggered tire setup, as Porsche has decided to do with the boxter and 911, but I'll mitigate the issue as much as possible in the meantime.

Similar to lift off oversteer, corner entry is a bit sketchy on the brakes. Braking must be done before corner entry. The Goblin doesn't like trail-braking one bit. I adjusted the brake proportioning valve a bit more (I'm now probably 2.5 turns in from max), but that didn't help a ton, as I was well under the braking threshold anyway.

Finally, it's down on horsepower just a bit, which I never thought I'd say. 0-60mph it's a real missile, but as speeds get up close to 100mph, the goblin runs out of steam and aerodynamic grace. Corvettes blow by easily at the end of front stretch.

Still, every car that outran it was either $100k and up, or a full race prepped car that was obviously dialed in. The goblin did well for it's first track day. Consumables are cheap, and it's a ton of fun to drive hard, if maybe just a bit scary. It's hard to ask for more from a $20k car you built yourself in your garage.

 

[Lndshrk Steve]

Track update! The goblin saw the track for the first time last week (Heartland Park, Topeka). I've autocrossed it before, but never had it on the big track. I ran with the Advanced group because intermediate was full, and it worked out fine. I was one of the slower guys, but not the slowest, and the A group generally knows what they are doing so it was a non issue.

THe goblin did fine, but more tweaks are needed (aren't they always?). It didn't explode, and I didn't crash it, so it was a successful day. I did spin it once though....lift off oversteer is real! Any MR2 driver will tell you, don't lift mid corner. It applies to the goblin. It will snap oversteer in a heartbeat, and I was too slow to catch it once. I altered tire pressures a bit, and firmed up the front suspension a bit, and it helped the issue. I suspect the real answer is to put on a staggered tire setup, as Porsche has decided to do with the boxter and 911, but I'll mitigate the issue as much as possible in the meantime.

Similar to lift off oversteer, corner entry is a bit sketchy on the brakes. Braking must be done before corner entry. The Goblin doesn't like trail-braking one bit. I adjusted the brake proportioning valve a bit more (I'm now probably 2.5 turns in from max), but that didn't help a ton, as I was well under the braking threshold anyway.

Finally, it's down on horsepower just a bit, which I never thought I'd say. 0-60mph it's a real missile, but as speeds get up close to 100mph, the goblin runs out of steam and aerodynamic grace. Corvettes blow by easily at the end of front stretch.

Still, every car that outran it was either $100k and up, or a full race prepped car that was obviously dialed in. The goblin did well for it's first track day. Consumables are cheap, and it's a ton of fun to drive hard, if maybe just a bit scary. It's hard to ask for more from a $20k car you built yourself in your garage.

Yes, I will SNAP oversteer if you SNAP off the throttle. You are moving the weight to the front and taking it all off the rear. You may be able to decelerate a little but mid engine cars LOVE to be on throttle thru the corners.
You may not want to trail brake but try turning in with the brake on. When driving formula cars, I would save a little braking for the turn in. Using the loaded front end and lightened rear end to rotate the car into the corner. I always would think, there is no use going faster in the wrong direction. I would stay on the brake until my hands stop turning the steering wheel. That's something else. Get your steering done at the turn in so you feel confident about your line thru the corner and you can stay on the throttle.